What action can prevent the degradation of blood samples prior to analysis?

Mixing with reagents is the correct action that can prevent the degradation of blood samples prior to analysis. This process can stabilize the constituents of the blood, such as enzymes and other biological markers that might otherwise break down or react adversely with the surrounding environment. Certain reagents are specifically designed to halt enzymatic activity or protect against oxidation, which is critical in preserving the integrity of the sample for accurate testing.

In contrast, freezing, while it can in some cases preserve biological samples, may not be suitable for all types of blood analysis and can lead to hemolysis or damage to blood cells if not done correctly. Air drying can lead to significant contamination and loss of sample integrity as components begin to degrade or react with environmental factors. Storing under light can also promote degradation, as some substances are sensitive to light exposure, leading to potential alterations in the sample composition. Therefore, mixing with appropriate reagents specifically targets the preservation of blood samples effectively for subsequent analysis.